This proposal is to further study relationships between structure and function in protein hormones displaying mammotropic and somatotropic activities. Human somatotropin (HGH), human choriomammotropin (HCS, HPL) and ovine prolactin will be investigated in their native forms as well as following chemical or enzymatic modification. The conformations of the various molecules will be assessed by ultraviolet absorption fluorescence and circular dichroism spectra. Conformational stability will be examined by differential scanning calorimetry. Functional properties will be investigated by radioimmunoassay, radio-receptor assay and classical in vivo bioassay techniques. Attempts will be made to produce and study new analogues or hybrids of these molecules by assemblying various fragments through non-covalent interaction (complementation) reactions.